1. Field of the Invention
The present invention relates to a rotary head assembly for magnetic recording/playback and a method for manufacturing the same and, in particular, to a thin film magnetic head for use in a helical scan type magnetic recording/playback apparatus using a magnetic tape, a method for manufacturing the same, and a rotary head assembly using a thin film magnetic head.
2. Description of the Related Art
FIGS. 5A and 5B illustrate a conventional helical scan type magnetic recording/playback apparatus. FIG. 5A is a perspective view of a rotary drum, and FIG. 5B is a schematic diagram illustrating recording on a magnetic tape. FIGS. 6A and 6B are perspective views of magnetic heads for use in a conventional helical scan type magnetic recording/playback apparatus. FIG. 6A is a perspective view of a MIG head, and FIG. 6B is a perspective view of a laminate type head. FIGS. 7A and 7B are perspective views of conventional magnetic heads mounted to bases. FIG. 7A shows a single head consisting of a single MIG head, and FIG. 7B shows a combination head consisting of two MIG heads. FIGS. 8A and 8B illustrate a thin film magnetic head for use in a magnetic recording/playback apparatus such as a hard disk apparatus. FIG. 8A is a perspective view of a thin film magnetic head, and FIG. 8B is a main part plan view of FIG. 8A. FIGS. 9A, 9B and 9C illustrate a rotary head assembly when the thin film magnetic head of FIGS. 8A and 8B is applied to a helical scan type magnetic recording/playback apparatus. FIG. 9A is a perspective view of a thin film magnetic head mounted to a base, FIG. 9B is a side view of a thin film magnetic head mounted to a rotary drum, and FIG. 9C is a schematic diagram illustrating recording on a magnetic tape by a thin film magnetic head. FIGS. 10A and 10B are side views of the rotary head assembly mounted to a rotary drum. FIG. 10A is a side view when the mounting is effected with the base inclined, and FIG. 10B is a side view when the surface for mounting the thin film magnetic head to the base is inclined.
In a magnetic recording/playback apparatus in which a magnetic tape is used as the magnetic recording medium, such as VCR or a data recording/playback apparatus for a computer, a helical scan type recording/playback is performed. In the helical scan type recording/playback, a so-called azimuth recording/playback is conducted, in which the track of the magnetic gap of the magnetic head is inclined with respect to the magnetic tape running direction, and in which the magnetic gap of the magnetic head is inclined by a predetermined angle (azimuth angle) with respect to the width direction of the track.
Generally speaking, in a helical scan type magnetic recording/playback apparatus, a plurality of heads are used in order to achieve an improvement in recording density and data transfer rate. For example, as shown in FIG. 5A, two magnetic heads H1 and H2 are arranged at opposed positions in a rotary drum D. The magnetic heads H1 and H2 may consist of a single head in which play back is performed by a single playback head on a track on which recording has been effected with a single recording head, or a combination head in which two recording heads and two playback heads are used. In either case, a so-called guard bandless type recording is performed, in which when the rotary drum D is driven and one of the magnetic heads H1 and H2 performs recording on the magnetic tape Tp, the track on which recording is performed overlaps a part of the region of another track on which recording has been performed immediately before that by the other magnetic head. For example, as shown in FIG. 5B, after recording is performed on the track T1, recording is performed on the track T2, overlapping a part of the region at the upper end of the track T1.
In both the single head and the combination head, a double azimuth system is adopted, in which the azimuth angles xcex81 and xcex82 of the magnetic gaps G1 and G2 of the magnetic heads H1 and H2 are inclined in directions opposite to each other. This is for the purpose of removing crosstalk with the adjacent track T2 by utilizing the azimuth loss based on the difference between the azimuth angle xcex81 of the track T1 and the azimuth angle xcex82 of the track T2. Although in the track T1 on which playback is performed by the magnetic head H1, there is a region where it overlaps another adjacent track T2 on which recording has been performed by the magnetic head H2. Further, at the time of playback on the track T2 by the magnetic head H2 also, the crosstalk with the adjacent track T1 is similarly removed due to the azimuth loss.
As a magnetic head used in a helical scan type magnetic recording/playback apparatus, there has been conventionally used a MIG (metal-in-gap) head as shown in FIG. 6A or a laminate type head as shown in FIG. 6B. In the MIG head shown in FIG. 6A, two half bodies Hm1 and Hm2, each of which is composed of a core 51 formed of magnetic material such as ferrite, a thin film 52 provided on the abutting surface of the core 51 and consisting of a metal magnetic material, and a coil 53 wound around the body of the core 51, abut each other. A magnetic gap Gm is formed on the surface on the thin film 52 is provided through the intermediation of a non-magnetic material such as glass. The laminate type head shown in FIG. 6B comprises two half bodies Hp1 and Hp2, each of which is composed of two substrates 54 formed of a non-magnetic material such as crystallized glass, a laminate film 55 provided between the two substrates 54 and consisting of a plurality of layers of a magnetic material and a non-magnetic material, and a coil 53 wound around the body portion of each of them, abut each other. A magnetic gap Gp is formed at the abutting surfaces through the intermediation of a non-magnetic material such as glass.
In the MIG head shown in FIG. 6A, the abutting surfaces of the half bodies Hm1 and Hm2 are machined, and the width of the magnetic gap Gm is made a desired minute width, making it the recording/playback track width. The half bodies Hm1 and Hm2 are caused to abut each other after machining the abutting surfaces inclined in the track width direction, and an azimuth angle xcex8m is provided in the magnetic gap Gm. Further, in the laminate type head shown in FIG. 6B, the track width is determined by the thickness of the laminate film 55, so that there is no need to perform the machining process for determining the track width as in the MIG head Hm. The half bodies Hp1 and Hp2 are caused to abut each other after grinding the abutting surfaces inclined with respect to the track width direction, and an azimuth angle xcex8p is provided in the magnetic gap Gp. In both the MIG head and the laminate type head, in the case of the double azimuth system, two magnetic heads of different and opposite azimuth angles xcex8m and xcex8p are prepared.
As shown in FIGS. 7A and 7B, one or two magnetic heads H1, H2, consisting of MIG heads, laminate type heads, etc., are mounted to the end portion of a base 56 on which a circuit board (not shown) is provided, and the end portion of the coil 53 and the circuit board (not shown) are connected. FIG. 7A shows a single head consisting of a single MIG head, and FIG. 7B shows a combination head consisting of two MIG heads arranged side by side. The magnetic heads H1 and H2 are mounted to the base 56 to form a rotary head assembly, and the coil 53 is connected through the circuit board (not shown) to an external processing circuit (not shown) for controlling the transmission and reception of signals. As shown in FIG. 5A, the rotary head assembly is mounted to opposed positions of the rotary drum D such that the magnetic gaps G1 and G2 are exposed on the outer peripheral surface of the rotary drum D.
Recently, in VCR and data recording/playback apparatus, to realize a high density in recording on a magnetic recording medium, a reduction in track width and an increase in frequency is effected. To achieve a reduction in track width, it is necessary to reduce the width of the magnetic gap. However, in the above-described MIG head, in which the magnetic gap Gm is formed by grinding, it is necessary to achieve a reduction in size, but a reduction in track width cannot be realized. To achieve a reduction in track width, a high grinding accuracy is required for the abutting surfaces for forming the magnetic gap Gm. However, an improvement in the machining accuracy in the minute magnetic gap Gm is hard to achieve. Further, to realize an increase in frequency, it is necessary to reduce the inductance. However, in the MIG head and the laminate type head, it is impossible to achieve a reduction in inductance. Further, in the MIG head and the laminate type head, the playback output cannot be enlarged when an increase in recording density is effected.
In a magnetic recording/playback apparatus, such as a hard disk apparatus, various types of thin film magnetic head are already used. Examples of the generally used thin film magnetic head include an induction type magnetic head mainly intended for recording (inductive head) and a magneto-resistive type magnetic head (MR head) for playback. A composite type thin film magnetic head formed by stacking the heads together is widely used. As shown in FIGS. 8A and 8B, a thin film magnetic head 61 used in a magnetic recording/playback apparatus, such as a hard disk apparatus, is formed by providing, on the side surface of a slider 62 obtained by cutting a wafer consisting of a ceramic material such as alumina titan carbide (Al2O3/TiC), a head element portion 63 composed of an MR head 63a and an inductive head 63b stacked thereon. Bonding pads 64 are connected to the MR head 63a and the inductive head 63b. The MR head 63a comprises an MR layer 63a1, an upper gap layer 63a2 provided over it, and a lower gap layer 63a3 provided under the slider 62 side. A magneto-resistive effect element (MR element) Ga is set by the thickness of the sum total of these three layers. The inductive head 63b comprises an upper core layer 63b1 and a lower core layer 63b2, a recording magnetic gap Gb is determined by the thickness of a non-magnetic material layer 63b3 provided therebetween. Further, due to the laminate structure, the MR element Ga and the magnetic gap Gb exposed on the upper surface of the slider 62 are parallel to each other. Further, the four bonding pads 64 provided on the side surface of the slider 62 are respectively connected to coils (not shown) of the MR layer 63a1 of the MR head 63a and the inductive head 63b by four lead-out lines (not shown).
This thin film magnetic head can be mass-produced at one time by a thin film formation process. As such, the thin film magnetic head obtained is advantageously of small size and of high recording/playback accuracy. Further, the thin film magnetic head can be easily adapted to a reduction in size, such as a reduction in gap width for a reduction in track width, and it is possible to realize an increase in recording density. Further, regarding the MR head in particular, it is possible to directly respond to a signal magnetic field independently of the relative speed of the magnetic recording medium, making it possible to effect high playback output. Moreover, since the inductance is far lower as compared with that of the MIG head and the laminate type head, it is possible to cope with an increase in frequency. In this way, the problems in the conventional magnetic head can be eliminated, so that there has been a demand for mounting the thin film magnetic recording head on a rotary head and apply it to a helical scan type magnetic recording/playback apparatus using a magnetic tape.
To apply the thin film magnetic head to a helical scan type magnetic recording/playback apparatus using a magnetic tape, there is prepared a thin film magnetic head 61 as shown in FIG. 9A, which is provided with an MR element Ga and a magnetic gap Gb on the side, and it is mounted to a base 65. A circuit board 66, such as a flexible printed circuit board connected to an external processing circuit, is provided in the same plane, and the terminal portions 66a thereof and the bonding pads 64 are connected by balls 67 formed by ball bonding. The rotary head assembly thus formed is mounted to opposed positions of the rotary drum D such that, as shown in FIG. 9B, the MR element Ga and the magnetic gap Gb are directed to the outer peripheral surface of the rotary drum D.
When performing recording/playback on a magnetic tape using this thin film magnetic head 61, azimuth recording/playback is indispensable, so that it is necessary to incline the MR element Ga and the magnetic gap Gb by a predetermined azimuth angle with respect to the track width direction. However, when the thin film magnetic head used in the above-described hard disk apparatus or the like is applied as it is, the MR element Ga and the magnetic gap Gb are perpendicular to the mounting surface of the base 65, as shown in FIG. 9B. When performing recording/playback by the thin film magnetic head 61 as shown in FIG. 9C, it is perpendicular to the track T, and the azimuth angle is zero. This is due to the fact that the thin film magnetic head 61 is obtained by a production process in which layers are sequentially stacked on the upper surface of a wafer, so that it is difficult to produce the head correctly inclining the MR element Ga and the magnetic gap Gb by a desired azimuth angle on the end surface of the slider 62, which is the upper surface of the wafer.
When providing an azimuth angle in the magnetic gap of a thin film magnetic head, it might be possible, as shown in FIG. 10A, to mount the base 65 mounted on the thin film magnetic head 61 to the rotary drum D in a state inclined by a desired azimuth angle by an appropriate means. Or, as shown in FIG. 10B, it might be possible to perform grinding on the surface of the base 65 mounted to the rotary drum D (the surface opposite to the surface on which the thin film magnetic head 61 is mounted) and incline the surface by a desired azimuth angle.
In the means shown in FIG. 10A, it is necessary for the azimuth angle of the MR element Ga and the magnetic gap Gb of the individual thin film magnetic head 61 and the mounting position with respect to the rotary drum D to be correct. Furthermore, in the means for mounting the base 65 in an inclined state, it is very difficult to reproduce with high accuracy the inclination angle and the mounting positions of the MR element Ga and the magnetic gap Gb. Additionally, in the means for forming inclination by grinding shown in FIG. 10B, the number of procedures increases, which leads to complexity, and it is very difficult to reproduce the inclination angle with high accuracy.
Accordingly, it is an object of the present invention to provide a thin film magnetic head for use in a helical scan type magnetic recording/playback apparatus which includes an MR head and an inductive head, in which an azimuth angle is provided in the magnetic gap, and which uses a magnetic tape, and a method for producing the same, and a rotary head assembly using a thin film magnetic head.
To achieve the above object, there is provided, in accordance with the present invention, a thin film magnetic head comprising a head element portion stacked on a side surface of a substrate having two opposed planes, two opposed side surfaces intersecting the planes, and a tape slide surface provided at one end portion of the planes and the side surfaces, at least one of a magnetic gap of an induction type magnetic head and a magneto-resistive effect element of a magneto-resistive effect type magnetic head being exposed on the tape slide surface, and a bonding pad connected to the head element portion, wherein an angle made by one of the side surfaces on which the head element portion and the bonding pad are provided and one of the planes constitutes an azimuth angle.
Further, in the thin film magnetic head of the present invention, the two planes and the two side surfaces of the substrate are respectively parallel to each other.
Further, in the thin film magnetic head of the present invention, there is provided a protecting plate attached so as to cover the head element portion to protect the head element portion.
In accordance with the present invention, there is further provided a thin film magnetic head producing method comprising the steps of: stacking on a planar wafer at least one of an induction type magnetic head and a magneto-resistive effect type magnetic head to form a plurality of head element portions, forming a plurality of sets of bonding pads connected to the head element portions, cutting the wafer with magnetic gaps of the head element portions being exposed on a same end surface to form a bar on which a plurality of said head element portions and said bonding pads are arranged side by side, attaching a protective member consisting of a bar-like non-magnetic material so as to stride over and cover the plurality of head element portions of the bar, and integrally cutting the bar and the protective member for each head element portion and each bonding pad to form a substrate and a protective plate with a set of said head element portion existing therebetween. An angle made by the cut surface and the surface on which the head element portion is provided constitutes a desired azimuth angle.
In accordance with the present invention, there is further provided a rotary head assembly, wherein one of the planes of the thin film magnetic head is placed so as to be in contact with the upper surface of a base consisting of a plate-like member, and an azimuth angle is determined by one of the side surfaces on which the head element portion and the bonding pad are provided and the upper surface of the base.
Further, in the rotary head assembly of the present invention, the angle formed by one of the side surfaces on which the head element portion and the bonding pad are provided and the base on the side where the head element portion and the bonding pad are provided is an obtuse angle.
Further, in the rotary head assembly of the present invention, two heads are arranged side by side, such that one of the planes of the thin film magnetic head is in contact with the upper surface of the base, where the base consists of a plate-like member. The azimuth angle of each of the two thin film magnetic heads is determined by the angle made by one of the side surfaces on which the head element portion and the bonding pad are provided and the upper surface of the base.
Further, the rotary head assembly of the present invention is placed on the base such that one of the side surfaces of one of the thin film magnetic heads on which the head element portion and the bonding pad are provided is not opposed to the side surface of the other thin film magnetic head.
Further, the rotary head assembly of the present invention is placed on the base such that one of the side surfaces of the one of the thin film magnetic heads on which the head element portion and the bonding pad are provided is opposed to one of the side surfaces of the other thin film magnetic head on which the head element portion and the bonding pad are provided. The angle that is formed by one of the side surfaces on which the head element portion and the bonding pad are provided and the base on the side where the head element portion and the bonding pad are provided is an obtuse angle.